Ai c aft impose th ee dema ds o a came a that most g ou d i stallatio s do ot. The came a moves, so eve y exposu e must be sho t e ough to limit blu . The ai f ame vib ates, so a se so that eads the pictu e ow by ow be ds ve tical li es a d wobbles the image. A d the softwa e that uses the pictu e, whethe it t acks featu es to estimate motio o compa es f ames to fi d a c ack, depe ds o geomet y. A disto ted f ame gives a disto ted estimate, a d the e o is ha d to tell f om eal moveme t. Desig e s the efo e t eat the shutte as a avigatio compo e t, ot as a cosmetic featu e.
Colo is a ely the poi t. Navigatio a d most i spectio algo ithms wo k o b ight ess. A colo came a pays fo colo with light a d with esolutio . The filte a ay i f o t of the se so abso bs pa t of the i comi g light, so each pixel collects less sig al, a d the came a must i te polate two-thi ds of its colo values to build a full image, which softe s fi e detail a d ca c eate colo f i ges at sha p edges. Fo softwa e that ig o es colo , those costs buy othi g, a d a mo och ome se so avoids them.
Light flicke s too. Flights i doo s, i wa ehouses, tu els, a d u de st uctu es use a tificial lighti g powe ed by the mai s supply, a d fluo esce t a d LED lamps flicke at twice the supply f eque cy. A came a with the w o g exposu e time shows da k ba ds olli g th ough the f ame, which co fuses featu e t acke s. A came a that ha dles flicke i its ow p ocesso spa es the flight compute . Ha dli g flicke i the came a also keeps the behavio the same o eve y host.
The li k is the fou th limit. Small flight compute s co ect came a modules ove USB, a d the ba dwidth of the li k co st ai s esolutio a d f ame ate. Teams that discove these limits afte the payload is built must cha ge the came a, the compute , o the softwa e, which is slow a d costly i a p og am with st ict weight a d powe budgets. A sho t calculatio of data ate, a ge, a d weight at the sta t avoids most of that ewo k.
The Falco -234MGS is built o the O semi AR0234, a 2MP (1920 x 1200) global shutte se so with a 1/2.6 i ch optical fo mat a d 3.0 mic o pixels, i a mo och ome co figu atio . The global shutte exposes a d holds eve y pixel at the same i sta t a d the eads them out, so motio a d vib atio do ot be d the pictu e. The 3.0 mic o pixels a e la ge fo a 2MP se so , a d with o colo filte a ay they collect oticeably mo e light, which allows sho te exposu es. Without demosaici g, eve y pixel is a eal lumi a ce measu eme t, so the full 1920 x 1200 g id co t ibutes to detail. The ext a ows beyo d a 16 by 9 f ame also leave oom fo elect o ic stabilizatio o c oppi g.
A sho t calculatio shows why exposu e time matte s i flight. With 3.0 mic o pixels a d a example 6 millimete le s, a ai c aft at 30 mete s sees about 1.5 ce timete s of g ou d pe pixel. At 10 mete s pe seco d, the ai c aft moves 1 ce timete du i g a 1 milliseco d exposu e, which is about two-thi ds of a pixel of motio blu , a d 5 ce timete s du i g a 5 milliseco d exposu e, which is mo e tha th ee pixels. The umbe s a e illust ative a d depe d o the le s, but they show why a se so that collects mo e light, a d ca the efo e use sho te exposu es, helps avigatio a d i spectio . Sixty f ames pe seco d also keeps the moveme t betwee f ames small, which makes featu es easie to t ack. Teams ca choose a faste mode whe the ai c aft flies quickly o tu s sha ply, a d they ca etu to Full HD fo the i spectio pass that follows, si ce the modes cha ge i softwa e without a y ha dwa e cha ge.
The data ates explai the choice of fo mat. Y8 sto es o e byte pe pixel. A 1080p f ame is about 2.1 megabytes, so 60 f ames pe seco d eeds about 124 megabytes pe seco d, o about 1 gigabit pe seco d. At 720p a d 60 f ames pe seco d, the st eam eeds about 55 megabytes pe seco d, a d at VGA a d 90 f ames pe seco d, about 28 megabytes pe seco d. A 4:2:2 colo fo mat uses two bytes pe pixel a d would eed twice as much. USB 2.0 ca ies at most 480 megabits pe seco d, with p actical th oughput of oughly 35 to 40 megabytes pe seco d, so o ly the VGA st eam would fit, while USB 3.0 has oom fo all th ee. The came a the efo e uses a USB 3.0 i te face, a d the Y8 fo mat keeps the st eam compact. Teams should still measu e th oughput o the eal flight compute , si ce the host affects the esult.
The o boa d ISP fi ishes the image i side the module. It applies de oisi g, gamma co ectio , auto exposu e, a d a ti-flicke fo 50Hz a d 60Hz supplies, which matches the exposu e time to the flicke pe iod of mai s lighti g a d emoves ba di g. The module is UVC complia t, so Wi dows, Li ux, a d A d oid hosts ca ope it without a p op ieta y d ive , a d it uses a S-Mou t (M12) le s holde . A global shutte emoves olli g shutte skew, but it does ot emove le s disto tio , which comes f om the optics, so teams that eed a ectili ea image should choose the le s a d a calib atio step togethe . A p i ted checke boa d a d a sho t calib atio outi e usually give a good esult.
Exposu e st ategy dese ves a sho t ote, because the be efits of a mo och ome global shutte se so depe d o how the came a is co figu ed. Auto exposu e follows the sce e as the ai c aft moves f om b ight sky to da k g ou d, a d it keeps exposu e times sho t whe the light allows. Teams that wa t epeatable motio blu ca cap the exposu e time a d let gai make up the diffe e ce, accepti g some oise i etu fo sha pe f ames. Flights u de a tificial lighti g should keep the a ti-flicke setti g matched to the supply f eque cy, so that the exposu e time stays a multiple of the flicke pe iod. Le s ape tu e matte s as well, si ce a faste le s lets the came a use sho te exposu es i the same light, at the cost of a shallowe depth of field a d mo e edge abe atio . These a e o di a y choices i ai c aft imagi g, a d Vadzo ca suggest sta ti g values fo exposu e limits a d a ti-flicke du i g evaluatio , so that the fi st test flight p oduces useful footage.
